Please enable JavaScript.

Unit 8
(The Earth) (Unit 8.1 (Rocks, Minerals & Soils (Geologists…

Geologists study a number of different materials that they call 'rocks'. Rocks are made up of grains of different materials called minerals. When you look closely at the rocks you can see them.

Each mineral is made of one chemical substance.the are 3 minerals that are in a rock called Granite, they are quartz,feldspar and mica.

Soil is made up of small particles of rock and minerals. Soil also contains the remains of plants ,animals and waste.

Unit 8.2

Soil

Soil is made up of pieces of rock and minerals, humus, bacteria,fungi and small animals.Some soils allow water to pass through very quickly where other soils may hold the water for a while.Drainage of water is important for the survival of crops. Farmers sometimes treat the soils to help them grow the crops they need.

Soils that have poor drainage have particles of sticky clay which are very small and closely packed together which holds water.

Unit 8.3

Igneous Rocks

The crust of the earth is made of solid rock but deep inside the earth it is very hot. When rock gets very hot it melts to form liquid. Beneath the crust the rock is molten( magma ).

When magma cools it turns into rock.Rocks that have been made this way is called 'Igneous Rocks'.

When magma cools underground, it cools very slowly because it's very hot down there. This gives time for crystals to grow on the rocks and change it into a different type of rock instead..

Unit 8.4

Sedimentary Rocks

Rivers often carry lots of sediment. Sediment is made of little tiny rocks that have been broken down. Layers of fragments of rocks or mud are collected on the sea bed. As more layers build upon top of them, the weight from the new layers presses down the particles deeper creating rock.

Limestone is a sedimentary rock formed from little fragment of shells from animals.

Unit 8.5

Metamorphic Rocks

Rocks sometimes get buried deep underground where it is very hot and the pressures are high. The high temperatures and pressures change the rocks. T hey squash the grains together to make the rock harder. The rock will have no gaps making it no longer porous. Rocks that have changed like this are metamorphic rocks.

Metamorphic rocks can also be formed when hot lava flows to close to the rocks near the surface of the earth. The heat from the lava makes the rock change.

Unit 8.6

Weathering

Rocks do not stay the same forever. They get worn away slowly with rain, wind,frost and temperature changes. when rocks are worn away by these things it is called weathering.

Chemical weathering is when there is too much pollution in the air that when it rains it rains acid. Physical weathering is when water gets into spaces and cracks in rocks and when it freezes it expands. This causes it to crack more and more.